Why does an email show up on my desktop IMac but not on my Iphone6 plus? - 1

Why does an email show up on my desktop IMac but not on my Iphone6 plus?

If you have set it up correctly then it should. Have you set up the iPhone to receive emails? You need to use the same credentials as the iMac and you need to enable the email account on your iPhone 6+ (settings, Accounts and passwords, then add your account or click on the account and enable)

Alternatively, if you have set up your emails to IMAP, if you have read and deleted the email on the iMac, then it won't appear in your inbox on the iPhone, it will appear in the deleted folder in your mail box (as in the iMac). This is normally how IMAP works.

Do you have your e-mail account set up to download messages from the server? If so, once you view that message on your iMac, it then resides on it's hard drive.